Apparatuses and methods for monitoring tendons of steerable catheters

ABSTRACT

Methods and apparatuses for detecting tension on a tendon and/or mechanical deformation (e.g., breakage) of one or more steering tendon of a steerable and flexible articulating device. Theses apparatuses may have one or more tendons that are each electrically conductive and configured to steer the apparatus when tension is applied to the proximal end of the tendon. Tension and/or breakage (or other deformation) of one or more of these tendons may be detected by monitoring the electrical resistance of the tendons.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/696,906, filed Nov. 26, 2019, which is a continuation of U.S. patentapplication Ser. No. 15/660,736, filed Jul. 26, 2017, which is acontinuation of U.S. patent application Ser. No. 15/084,984, filed Mar.30, 2016, which claims the benefit of U.S. Provisional Application No.62/140,344, filed Mar. 30, 2015, which application is incorporatedherein by reference.

The present invention relates to medical instruments, tools, and methodsthat may be incorporated into a robotic system, such as those disclosedin U.S. patent application Ser. No. 14/523,760, filed Oct. 24, 2014,U.S. Provisional Patent Application No. 62/019,816, filed Jul. 1, 2014,U.S. Provisional Patent Application No. 62/037,520, filed Aug. 14, 2014,U.S. Provisional Patent Application No. 62/057,936, filed Sep. 30, 2014,U.S. Provisional Patent Application No. 62/096,825, filed Dec. 24, 2014,and U.S. Provisional Patent Application No. 62/134,366, filed Mar. 17,2015, the entire contents of which are incorporated herein by reference.

FIELD OF THE INVENTION

The apparatuses (including systems and devices) described herein may berelated to steerable elongate devices. In particular, described hereinare tendon-steerable elongate members suitable for medical applicationsin which tension and/or breakage of one or more tendons used to steerthe device may be sensed.

BACKGROUND

Bending of elongate members such as steerable catheters allows thesedevices to be used in many beneficial ways, including when performingsurgical procedures. For a catheter (and similar elongate, bendablemembers), articulation may be achieved by tensioning a tendon (alsoreferred to herein as pull wire) which runs the length of the device,and is typically attached at the distal end, so that it can be actuatedproximally. In a device with free floating tendons, wherein the tendonsare not pre-tensioned, a certain level of slack within the catheter willlikely exist. To remove the slack consistently, a tensioning algorithmbased on measured force on the wire may be used. However, sensor sizeand placement can result in noise or inaccurate readings. Likewise, inthe event of a wire breakage, external force sensors may detect a dropof tension on a wire, but may be unreliable, and may increase thecomplexity, size, and cost for the catheter.

One alternative to a traditional strain gauge is a resistance wiretension measuring gauge, such as described in U.S. Pat. No. 4,803,888,in which the electrical resistance of a wire was found to be related tothe strain on the wire. To date, however, adapting such resistancemeasuring wires for us as part of a steerable guidewire has not beendescried and/or successfully achieved. This may be due to the relativecomplexity of the tendon-drive elongate members, including the need forsmall diameters and the difficulty in accurately delivering power to thewire(s) acting as a strain gauge and the uncertainty associated withdetecting a robust change in resistance with materials useful as tendons(wires) in steerable elongate members useful for medical applications.

Thus, it would be useful to provide tendon-steerable elongate devicessuch as catheters in which the tension on the tendon may be easily andaccurately detected. Described herein are elongate, steerable devices,such as catheters, that are configured to directly measure the wiretension, as well as reliably detect wire breakage.

BRIEF SUMMARY

In general, described herein are tendon-steerable elongate apparatuses,and particularly medical apparatuses, that may be configured to easilyand accurately detect strain on the tendons. Although the examples oftendon-steerable elongate devices provided herein are primarily elongatecatheters for medical use, the features, principles and methodsdescribed herein may generally be adapted for use with any elongatetendon-steerable member, including steerable guidewires, sleeves,probes, or the like. Thus, the term “catheter” recited herein may referto any type of elongate and tendon-steerable apparatus, includingguidewires, sleeves, probes, etc.

Any of the apparatuses described herein may be a device and/or system(e.g., a related or interaction set of devices). For example, describedherein are elongate catheter apparatuses having a plurality of tendonsthat are configured to be tensioned (e.g., pulled, and/or in somevariations, pushed) to steer the apparatus, e.g., by bending the distaltip region (or an intermediate region) of the apparatus. The tendons maybe electrically conductive (e.g., may comprise an electricallyconductive material, such as steel and other alloys, including shapememory alloys (e.g., Nitinol). The apparatus may include, or may beconfigured to interact with, a sensing circuitry that can be put intoelectrical communication with the electrically conductive tendons of theapparatus, so that the sensing circuitry may detect, and in some casesrespond to, tension on any of the tendons to which it is connected. Thesensing circuitry may be on the elongate medical device (e.g.,catheter), or it may be on a separate device that is placed inelectrical contract/communication with the elongate medical device. Forexample, described herein are driving units, such as catheter steeringunits, that include sensing circuitry, to detect tension on one or moretendons (wires) of an elongate medical device when the drivingunit/device is connected to a steerable elongate member such as asteerable catheter.

For example, described herein are steerable catheter systems thatinclude: a plurality of electrically conductive tendons extending alonga length of a steerable catheter; and a sensing circuit configured to bein electrical connection with the plurality of tendons, wherein thesensing circuit an electrical resistance of one or more tendon of theplurality of tendons.

Any of these steerable catheter systems may include: a steerablecatheter, the steerable catheter comprising a body having an elongatelength, a lumen extending through the elongate length, an electricallyconductive outer member extending along the elongate length of the body,and a plurality of electrically conductive tendons each extending alongthe length of the catheter and having a proximal end region and a distalend region, wherein the distal end region of each tendon is coupled to adistal portion of the body so that applying tension a tendon of theplurality of tendons actuates bending of the catheter, wherein theplurality of tendons are electrically connected to the electricallyconductive outer member at their distal end regions; and a sensingcircuit configured to be in electrical connection with the plurality oftendons, wherein the sensing circuit detects an electrical resistance ofone or more tendon of the plurality of tendons.

In some variations, the sensing circuit is configured to detect a changein the electrical resistance of the one or more tendons of the pluralityof tendons. For example, the sensing circuit may be configured toidentify a baseline electrical resistance for each tendon; this baselinemay be used to automatically and/or manually adjust the tension of atendon in the device.

The catheter may have any appropriate shape and/or additional features.For example, the catheter may comprise a body having an elongate lengthand one or more lumen extending through the elongate length. Thecatheter may include an electrically conductive outer member extendingalong the length of the steerable catheter.

The electrically conductive outer member may comprise a dedicatedconductive (wire) for delivering voltage. In some variations theconductive outer member is all or a portion of the housing of thecatheter, including a woven and/or braided outer layer of the braidwire.For example, in some variations, the catheter may include anelectrically conductive outer braided member extending along the lengthof the steerable catheter in electrical contact with a distal end of theplurality of electrically conductive tendons. In some variations theconductive outer member is an electrically conductive tendon configuredto deliver an electrical potential to a distal end of each tendon of the(other) plurality of tendons. In some variations, the electricallyconductive outer member comprises an electrically conductive outer braidconfigured to deliver an electrical potential to a distal end of eachtendon of the plurality of tendons.

As mentioned above, the tendons described herein may be used to actuatethe elongate (e.g., catheter) member. A tendon may be a wire that islinear and/or coiled, flat, round, helical, or the like. The tendon isgenerally formed of a conductive material (in whole or in part) thatchanges resistance as it is placed under tension, and has a reasonablehysteresis property so that after the release of tension, the shape andelectrical properties will return to pre-tensioned levels without unduedelay (e.g., within 5 seconds, 2 seconds, 1 second, less than 1 second,0.9 sec., 0.8 sec., 0.7 sec., 0.6 sec., 0.5 sec., 0.4 sec., 0.3 sec.,0.2 sec., 0.1 sec., etc.)

The tendons described herein may include a distal end region that may bemechanically coupled to a distal end region of the catheter so thatapplying tension to a tendon of the plurality of tendons bends thecatheter. Further, the distal end regions of each of the tendons of theplurality of electrically conductive tendons may be electricallyconnected to each other, e.g., so that the same stimulation energy(e.g., applied voltage) may be applied across all of the tendons.

In general, a sensing circuit used with the tendon-articulating devicesmay be integrated into the tendon-driven, e.g., at a distal end regionof the catheter. Alternatively or additionally, a sensing circuit may beincluded as part of a separate or separable driver. For example, thesystem may include a robotic driver unit configured to couple with theplurality of tendons and apply a proximal tension to the each of thetendons of the plurality of tendons; the sensing circuitry may beintegrated into the robotic driver unit.

For example, described herein are robotic driver devices configured tocouple with a plurality of tendons of a steerable catheter and apply aproximal tension to the each of the tendons of the plurality of tendons,the device comprising: a plurality of individually controllable driverseach configured to mechanically actuate a tendon of the plurality oftendons when the device is coupled with a catheter; a plurality ofelectrical contacts each configured to make an electrical connectionwith a tendon of the plurality of tendons when the device is coupledwith a catheter; and a sensing circuit connected to the plurality ofelectrical contacts and configured to detect an electrical resistance ofeach of the one or more tendons of the plurality of tendons. Thesedevices may include a voltage source configured to apply a bias voltageto an electrically conductive member of a catheter when the device iscoupled with the catheter. These devices may include a plurality ofsensing resistors of predetermined value, wherein each sensing resistoris in electrical communication with one of the plurality of electricalcontacts and further wherein the sensing circuit is configured tomeasure the voltage drop across the sensing resistors to detect theelectrical resistance of each of the one or more tendons of theplurality of tendons.

Any of the devices having a sensing circuit described herein may beconfigured to provide or evoke feedback when applying stimulation usingthe apparatus, e.g., to eliminate slack in the tendon. For example, afeedback circuit may be configured to control the tension applied toeach of the plurality of individually controllable drivers based on thedetected electrical resistance of each of the one or more tendons of theplurality of tendons when the device is coupled with a catheter.

Also described herein are steerable catheter devices configured to allowelectrical detection of tension or breakage of a steering tendon. Forexample, a steerable catheter device may include: a body having anelongate length extending proximally to distally; at least one lumenextending through the elongate length; an electrically conductive memberextending along the elongate length of the body; and a plurality ofelectrically conductive tendons each extending along the elongate lengthof the body and having a proximal end region and a distal end region,wherein the distal end region of each tendon is coupled to a distalportion of the elongate body so that applying tension to a tendon of theplurality of tendons actuates bending of the catheter; and wherein thedistal end region of each tendon of the plurality of tendons is inelectrical communication with the electrically conductive member.

In any of the apparatuses and methods described herein, the plurality ofelectrically conductive tendons may be electrically insulated.

In some variations, the steerable elongate device (e.g., catheter) mayinclude a wire terminator at the distal portion of the body, wherein thedistal end regions of each of the plurality of electrically conductivetendons terminates onto the wire terminator.

Methods of detecting the tension on and/or breakage of a tendon in anelongate and tendon-steerable medical device are also described herein.For example, described herein methods of detecting tension and breakageof a tendon in a steerable, elongate catheter. The method may include:applying an electrical potential along a tendon extending within thecatheter; applying proximal tension to the tendon to steer the catheter;sensing an electrical resistance of the tendon; and determining atension on the tendon or breakage of the tendon based on the electricalresistance of the tendon.

For example, described herein are methods of adjusting tension of atendon in a steerable, elongate catheter, the method comprising:applying an electrical potential along a tendon extending within thecatheter; sensing an electrical resistance of the tendon; and applyingproximal tension to the tendon to steer the catheter based on theelectrical resistance of the tendon.

In general, sensing an electrical resistance of the tendon may includemeasuring a voltage drop across a resistor having a predetermined value,wherein the resistor is electrically connected with the tendon.

The step of applying proximal tension may include applying tension basedon the electrical resistance of the tendon.

Determining the tension on the tendon or breakage of the tendon based onthe electrical resistance of the tendon may include determining thetension on the tendon or breakage of the tendon based on a change in theelectrical resistance of the tendon.

The systems and apparatuses for detecting (via resistance of the tendon)tension on the wires/tendons used to steer these apparatuses may beconfigured to automatically, allow for manually, or both automaticallyand/or manually allow adjustment of the tendon based on the results oflooking at tension (e.g., resistance) of the tendon. For example, theapparatus may be configured to regulate an amount of slack-reducingtension applied to the tendon based on the sensed electrical resistanceof the tendon.

As mentioned, in general, any of these methods may include determining atension on the tendon or breakage of the tendon based on the electricalresistance of the tendon.

A breakage may be detected by the apparatuses herein when, for example,the resistance of the tendon (or a group of tendons) rises steeply(e.g., appearing as an open circuit, with very, e.g., near infinite)resistance. If the sensing circuitry detects a breakage, it may triggeran alert when the sensed electrical resistance indicates that the tendonhas broken.

Any of the methods described herein may include connecting the catheterto a robotic driver unit, wherein the robotic driver unit is configuredto apply proximal tension to the tendon. For example, the methods mayinclude connecting the catheter to a robotic driver unit, wherein therobotic driver unit is configured to sense the electrical resistance ofthe tendon.

In general, applying an electrical potential may include applying avoltage, and in particular, applying a voltage to a distal end of thetendon from an electrically conductive outer member extending along alength of the catheter.

Also described herein are methods of detecting tension and breakage ofone or more tendon in a steerable, elongate catheter, the methodcomprising: applying an electrical potential along each of a pluralityof tendons extending within the catheter; applying proximal tension toone or more of the tendons of the plurality of tendons to steer thecatheter; sensing an electrical resistance of each of the tendons of theplurality of tendons; and determining a tension on at least one of thetendons of the plurality of tendons or breakage of at least one of thetendons of the plurality of tendons based on the electrical resistanceof the at least one of the tendons of the plurality of tendons.

For example, described herein are methods of adjusting tension of atendon in a steerable, elongate catheter, the method comprising:applying an electrical potential along a tendon extending within thecatheter; sensing an electrical resistance of the tendon; and applyingproximal tension to the tendon to steer the catheter based on theelectrical resistance of the tendon.

BRIEF DESCRIPTION OF THE DRAWINGS

The novel features of the invention are set forth with particularity inthe claims that follow. A better understanding of the features andadvantages of the present invention will be obtained by reference to thefollowing detailed description that sets forth illustrative embodiments,in which the principles of the invention are utilized, and theaccompanying drawings of which:

FIGS. 1A-1C schematically illustrates the operation of tendons (pullwires) to articulate a catheter and detect tension and/or breakage ofthe tendons. FIG. 1A illustrates a schematic example of a catheterhaving a pair of tendons fixed at the distal end, in which the tendonsare either not under tension or are under an equal amount of sleighttension (e.g., slack). FIG. 1B shows the apparatus of FIG. 1A withtension applied on the lower tendon to bend the distal end region down.

FIG. 1C shows the apparatus of FIG. 1A in which a tendon has broken. Inany of these examples, the resistance of the tendons may be used todetect tension and breakage.

FIG. 2A shows one example of a catheter having electrically conductivetendons configured to allow electrical detection of tension and asensing circuit.

FIGS. 2B and 2B1-2B2 are another example of a steerable catheter systemconfigured to allow electrical detection of the resistance of a tendonto detect tension and breakage.

FIGS. 2C and 2C1-2C2 are another example of a steerable catheter systemconfigured to allow electrical detection of the resistance of a tendonto detect tension and breakage, in which one of the tendons acts as theinput voltage.

FIGS. 3A-3B illustrates a system including a catheter and robotic driverconfigured to allow electrical detection of the resistance of a tendonto detect tension and breakage. In FIG. 3A the catheter is shown beinginserted into the robotic driver device, while FIG. 3B shows thecatheter inserted into the robotic driver.

FIG. 3C shows the distal end region of the catheter of FIGS. 3A-3B.

FIGS. 4A-4B illustrates an enlarged view of a distal end region of acatheter, similar to the variation shown in FIG. 3C.

FIGS. 5A-5B illustrate example of a robotic drive device configured toallow electrical detection of the resistance of tendons of a catheter todetect tension and breakage of the tendon(s).

FIGS. 6A-6B illustrate one example of measurement of tension from atendon wire showing the force applied to pull the tendon (FIG. 6A) andthe detected resistance (FIG. 6B) of the tendon. The minimal force forthe first half of the graph results from slack in the pull wire,resulting in a relatively constant (baseline) resistance for the tendon.

FIGS. 7A-7B show another example of tension being applied gradually to atendon (FIG. 7A), and the resulting measured change in resistance (FIG.7B).

FIGS. 8A-8B show another example of tension being applied gradually to atendon (FIG. 8A), and the resulting measured change in resistance (FIG.8B).

FIGS. 9A-9B show another example of tension being applied gradually to atendon (FIG. 9A), and the resulting measured change in resistance (FIG.9B).

DETAILED DESCRIPTION

Described herein are methods and apparatuses for detecting tension on atendon (e.g., wire, pull wire, or cable). In particular, theseapparatuses are steerable elongate apparatuses (generically, “flexiblearticulating devices”) having one or more tendon that is electricallyconductive and configured to bend (steer) the apparatus when tension isapplied to the proximal end of the tendon. For example, described hereinare methods and apparatuses for determining tension and/or breakage ofone or more tendons by monitoring the electrical resistance of thetendon.

As used herein determining and/or measuring and/or monitoring tension ofa tendon (also referred to herein as wires or pull wires) includesmonitoring stress/strain on tendon. In particular, the apparatus may beconfigured to detect and reduce slack on the tendon by applyingelectrical energy through the tendon and detecting a correspondingresistance, where the resistance of the tendon is reflective of themechanical load (tension, or stress/strain) on the tendon. For example,an apparatus as described herein may detect tension or monitor thestress/strain on the tendons (e.g., pull wires) by detecting the changein tendon resistance as tension is applied.

As will be described in greater detail below, this may include treatingthe tendon as a resistor of a circuit. When tension increases on thetendon, such as when the catheter is articulated or pushed againstanatomy, the tendon stretches and thus increases in electricalresistance. To determine whether a tendon is broken or not, continuityin the circuit is examined. If the circuit is closed, in which a signalcan pass through from the positive to negative terminal of the pullwire, then the tendon is intact. If the circuit is open, then a tendonhas broken.

For example, FIGS. 1A-1C show illustrations of a schematic apparatushaving a pair of tendons and further illustrates one example of a way tomonitor the status of a catheter 101. In FIG. 1A, the two tendons areconfigured as variable resistors in a circuit which measures thisresistance change; little if any tension is applied to the tendons, andthe catheter is unbent. In FIG. 1B, one tendon 103 is articulated, thereis an increase in tension, and thus a measurable increase in resistancethrough the articulated tendon. As shown in FIG. 1C, if a tendon breaks105, the resulting “circuit” including the length of the tendon is anopen circuit, e.g., so that the apparent resistance of the tendonapproaches infinite.

In general, the apparatuses described herein may include a metal tendon(pull wire), and a sensing circuit, as shown in FIG. 2A. In thisexample, the apparatus is a system including a catheter (a portion ofwhich is shown in FIG. 2A, including the elongate body). In thisexample, four tendons 201, 202, 203, 204 extending within the lengths ofthe elongate body forming the catheter. Each tendon may be present in achannel within the elongate body. The catheter body (elongate body) mayalso include one or more lumen. Each pull wire may be treated as avariable resistor (e.g., Rw1, Rw2, Rw3, and Rw4) and may be separatelyor collectively monitored by the sensing circuit 215 after connecting tothe sensing circuit (e.g., voltage measuring circuitry). In somevariations, the connection/interface with the sensing circuit mayinclude electrical contacts and known (fixed, predetermined value)resistors Rk across which the voltage drop may be measured. When aninput voltage 210 is applied to the distal end regions of each of thetendons (pull wires), the resulting voltage drop detected may be used todetermine the resistances of each of the tendons.

This is illustrated in different configurations in FIGS. 2B and 2C. Forexample, in FIG. 2B, the four tendons (pull wires 201, 202, 203, 204)are each mechanically and electrically connected at the distal endregion to an electrically conductive wire terminator 206, and an inputvoltage is connected to the wire terminator. The input voltage may bedelivered by any electrically conducive member; in FIG. 2B it is a wireextending proximally to the distal wire terminator. In some variationsthe input voltage (electrically conducive member or electricallyconductive outer member) is a part of the body of the catheter, such asa braid of the braided outer sheath. The proximal ends of each tendon(pull wires 201, 202, 203, 204) are connected to resistors 221, 222,223, 224 having a predetermined, known value. A sensing circuit 208 maybe connected to each tendon 201, 202, 203, 204 through electrical wires216; the sensing circuit 208 comprises voltmeters 211, 212, 213, 214which measure the voltage (Vm) across each known resistor (Rk) 221, 222,223, 224. From this configuration each of the resistances of the wires201, 202, 203, 204 may be determined, as illustrated in the equations ofFIG. 2B1, and an equivalent circuit is shown in FIG. 2B2.

Another example of a configuration that may be used to determine tensionand/or breakage of a tendon is shown in FIG. 2C. In this example, one ofthe tendons (pull wire 201) is configured to operate as an input voltage(electrically conductive member), electrically connecting to each of theother tendons (pull wires, 202, 203, 204) at their distal ends. Theproximal ends of the other tendons (pull wires 202, 203, 204) areconnected to each other in parallel and connected to a known resistor225 having a predetermined value, across which the voltage may bemeasured by the sensing circuitry to determine if a break has occurredin any of the tendons. An equivalent circuit for this is shown in FIG.2C2, and relevant equations are shown in FIG. 2C1.

Any of the sensing circuits described herein may be configured tocontinuously or periodically monitor the resistance through one or moreof the tendons 201, 202, 203, 204 when connected to the sensingcircuitry. For example, any of the sensing circuits described herein mayinclude a data acquisition card. The sensing circuit may be embeddedand/or integrated into the catheter or into the driver, e.g., in therobot-side of the catheter/robot interface. The connection from thetendon to the system may be made through a tendon (pull wire) pulley andmotor shaft, as illustrated in FIGS. 3A-3C and 4A-4B (showing a cathetersystem 300 comprising pull wires 310 enclosed within and coupled to anouter braid 320 through a control ring 320, the pull wires 310 beingoperatively coupled to a set of pulleys 340 and electrically connectedto voltmeters 350 through an electrical connection 360 at handle end orinstrument base 370) and 5A-5B (showing the pulleys 340 at the handleend or instrument base 370). Also, the positive (non-ground) terminal ofthe pull wires can be shared. The positive input is typically a constantvoltage (DC). The opposite (e.g., negative) terminal can be used tomeasure resistance with an Ohmmeter or current.

For example, FIGS. 5A and 5B illustrate a pull wire pulley 340 with ametal connector at the bottom, making electrical contact between thedrive unit and the electrically conducive tendon. When the pulley 340 isplaced onto the motor shaft of the drive unit 380, the electricalconnection from catheter tendon (pull wire 310) to the sensing circuit350 in the driver is made.

In one example, as shown in graphs 600 a, 600 b in FIGS. 6A-6B, acatheter tendon (e.g., 0.005″ steel) was attached to an ATI force sensoron one end and a linear slide on another. The linear slide was moved tostretch the pull wire and the resulting tension was recorded on the ATIand the resistance change was recorded on the multimeter. 8.2 N of forcecorresponded to 0.5 Ohms of resistance. The applied force is shown inthe graph 600 a in FIG. 6A, while the resistance measured from thesensing circuitry is shown in the graph 600 b in FIG. 6B. There isexcellent agreement between the two, and the dynamic range of theresistance is between about 0.4-0.6 Ohms for this example. As seen, fromabout 3 mm of strain, the ATI force sensor measured 8.2 N of force,while the tendon resistance changed by approximately 0.5 Ohm. The changein resistance was approximately linear. The minimal force for the firsthalf of the experiment is from slack in the pull wire. Thus the systemwas competent to detect when the first indication of force (when slackwas eliminated) at approximately 1000 samples in.

FIGS. 7A-7B, 8A-8B and 9A-9B illustrate graphs 700 a, 700 b, 800 a, 800b, 900 a, and 900 b, respectively, for other examples in whichtensioning force was applied to a tendon, such as a tendon that may beused with a catheter as described herein, and the electrical resistanceof the tendon reflected the tension and/or state (breakage, deformation,etc.) of the tendon. For example, in the graphs 700 a in FIG. 7A, theforce applied to a tendon was directly sensed by the change inresistance of the tendon, as seen in the graphs 700 b FIG. 7B. Likewise,in the graphs 800 a in FIG. 8A, up to 20 N of applied force (tension)was applied and detected by a change in the resistance of the tendon. Ingeneral, the sensing circuitry may include amplification and/orfiltering of the signals (and detected resistances). For example, in thegraphs 800 b in FIG. 8B, the somewhat noisy resistance signal is shownboth unfiltered and filtered (showing the smooth line within the rawsignal).

FIGS. 9A and 9B show graphs 900 a and 900 b, respectively, alsoillustrating the potential of this method to detect mechanical faults inthe tendons, such as breakage and/or deformation. As illustrated in thegraph 900 b in FIG. 9B, when force was applied (shown in FIG. 9A), adeformation of the pull wire (yielding of the pull wire) resulted in adetectable shift of the baseline of the resistance value measured.

Using existing tendons (pull wires) in a catheter to monitor the healthand performance of the device as described herein may be highlyadvantageous. For example, current state of the art tension sensing forcatheters require expensive strain gauges, motor current estimation, ortorque sensors. The methods and apparatuses described herein provide acost-effective way of obtaining the same information. The methods andapparatuses also utilize existing catheter features, and only require asmall modification to the catheter to system interface. In contrast, apiezoelectric strain gauge placed in-line with the pull wires wouldrequire additional wiring to the gauge.

In general, if a tendon underdoes excessive strain, it will exhibitpermanent deformation. This may be detected by large changes in theresistance-to-tension calibration, and can be used as an indicator forcompromised pull wire integrity, as illustrated above. In contrast,external sensors may only be able to estimate pull wire integrity. Inaddition, the methods and apparatuses described herein provide fastdetection and computation, and do not require algorithms to filter data,while still allowing constant monitoring.

As mentioned above, in some variations, the sensing circuit may bewithin the apparatus (e.g., catheter). Such system may then pass asignal, including a digital signal, to the driver or other processor,indicating the tension and/or breakage (deformation, etc.) of thetendon.

As illustrated above in FIG. 2C, in some variations a simplified versionof the method and/or apparatus may be used, in which tension sensing canbe eliminated in favor of just wire breakage detection. Such detectioncircuits may be made even simpler and less expensively.

When a feature or element is herein referred to as being “on” anotherfeature or element, it can be directly on the other feature or elementor intervening features and/or elements may also be present. Incontrast, when a feature or element is referred to as being “directlyon” another feature or element, there are no intervening features orelements present. It will also be understood that, when a feature orelement is referred to as being “connected”, “attached” or “coupled” toanother feature or element, it can be directly connected, attached orcoupled to the other feature or element or intervening features orelements may be present. In contrast, when a feature or element isreferred to as being “directly connected”, “directly attached” or“directly coupled” to another feature or element, there are nointervening features or elements present. Although described or shownwith respect to one embodiment, the features and elements so describedor shown can apply to other embodiments. It will also be appreciated bythose of skill in the art that references to a structure or feature thatis disposed “adjacent” another feature may have portions that overlap orunderlie the adjacent feature.

Terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the invention.For example, as used herein, the singular forms “a”, “an” and “the” areintended to include the plural forms as well, unless the context clearlyindicates otherwise. It will be further understood that the terms“comprises” and/or “comprising,” when used in this specification,specify the presence of stated features, steps, operations, elements,and/or components, but do not preclude the presence or addition of oneor more other features, steps, operations, elements, components, and/orgroups thereof. As used herein, the term “and/or” includes any and allcombinations of one or more of the associated listed items and may beabbreviated as “/”.

Spatially relative terms, such as “under”, “below”, “lower”, “over”,“upper” and the like, may be used herein for ease of description todescribe one element or feature's relationship to another element(s) orfeature(s) as illustrated in the figures. It will be understood that thespatially relative terms are intended to encompass differentorientations of the device in use or operation in addition to theorientation depicted in the figures. For example, if a device in thefigures is inverted, elements described as “under” or “beneath” otherelements or features would then be oriented “over” the other elements orfeatures. Thus, the exemplary term “under” can encompass both anorientation of over and under. The device may be otherwise oriented(rotated 90 degrees or at other orientations) and the spatially relativedescriptors used herein interpreted accordingly. Similarly, the terms“upwardly”, “downwardly”, “vertical”, “horizontal” and the like are usedherein for the purpose of explanation only unless specifically indicatedotherwise.

Although the terms “first” and “second” may be used herein to describevarious features/elements (including steps), these features/elementsshould not be limited by these terms, unless the context indicatesotherwise. These terms may be used to distinguish one feature/elementfrom another feature/element. Thus, a first feature/element discussedbelow could be termed a second feature/element, and similarly, a secondfeature/element discussed below could be termed a first feature/elementwithout departing from the teachings of the present invention.

As used herein in the specification and claims, including as used in theexamples and unless otherwise expressly specified, all numbers may beread as if prefaced by the word “about” or “approximately,” even if theterm does not expressly appear. The phrase “about” or “approximately”may be used when describing magnitude and/or position to indicate thatthe value and/or position described is within a reasonable expectedrange of values and/or positions. For example, a numeric value may havea value that is +/−0.1% of the stated value (or range of values), +/−1%of the stated value (or range of values), +/−2% of the stated value (orrange of values), +/−5% of the stated value (or range of values), +/−10%of the stated value (or range of values), etc. Any numerical rangerecited herein is intended to include all sub-ranges subsumed therein.

Although various illustrative embodiments are described above, any of anumber of changes may be made to various embodiments without departingfrom the scope of the invention as described by the claims. For example,the order in which various described method steps are performed mayoften be changed in alternative embodiments, and in other alternativeembodiments one or more method steps may be skipped altogether. Optionalfeatures of various device and system embodiments may be included insome embodiments and not in others. Therefore, the foregoing descriptionis provided primarily for exemplary purposes and should not beinterpreted to limit the scope of the invention as it is set forth inthe claims.

The examples and illustrations included herein show, by way ofillustration and not of limitation, specific embodiments in which thesubject matter may be practiced. As mentioned, other embodiments may beutilized and derived there from, such that structural and logicalsubstitutions and changes may be made without departing from the scopeof this disclosure. Such embodiments of the inventive subject matter maybe referred to herein individually or collectively by the term“invention” merely for convenience and without intending to voluntarilylimit the scope of this application to any single invention or inventiveconcept, if more than one is, in fact, disclosed. Thus, althoughspecific embodiments have been illustrated and described herein, anyarrangement calculated to achieve the same purpose may be substitutedfor the specific embodiments shown. This disclosure is intended to coverany and all adaptations or variations of various embodiments.Combinations of the above embodiments, and other embodiments notspecifically described herein, will be apparent to those of skill in theart upon reviewing the above description.

What is claimed is:
 1. A articulatable elongate member comprising: ashaft with an articulatable portion; and a first pull wire enclosedwithin the shaft and coupled to the shaft such that a first applicationof tension to the first pull wire articulates the articulatable portion,the first pull wire comprising a first proximal portion configured to beoperatively coupled to a robotic driver configured to apply tension tothe first pull wire to articulate the articulatable portion, and thefirst pull wire being electrically couplable to a sensing circuitrycoupled to the robotic driver and configured to measure a change to anelectrical resistance of the first pull wire, thereby indicating achange in tension or a breakage of the first pull wire.
 2. Thearticulatable elongate member of claim 1, wherein the sensing circuitryis integrated with the robotic driver.
 3. The articulatable elongatemember of claim 1, further comprising the sensing circuitry.
 4. Thearticulatable elongate member of claim 1, further comprising a secondpull wire enclosed within the shaft and coupled to the shaft such that asecond application of tension to the second pull wire bends the shaft,the second pull wire comprising a second proximal portion configured tobe operatively couplable to the robotic driver, the robotic driver beingconfigured to apply tension to the second pull wire to bend the shaft.5. The articulatable elongate member of claim 1, wherein the first pullwire is electrically couplable to a wire terminator on the shaft to forma circuit comprising the wire terminator, the first pull wire, and thesensing circuitry.
 6. The articulatable elongate member of claim 5,further comprising at least one resistor couplable to the first pullwire, the at least one resistor having a known electrical resistance,and wherein the circuit comprises the wire terminator, the first pullwire, the at least one resistor, and the sensing circuitry.
 7. Thearticulatable elongate member of claim 6, further comprising a secondpull wire enclosed within the shaft and coupled to the shaft such that asecond application of tension to the second pull wire bends the shaft,and wherein the at least one resistor comprises a first resistor and asecond resistor, the first and second pull wires being couplable to thefirst and second resistors, respectively.
 8. The articulatable elongatemember of claim 6, wherein the sensing circuitry comprises at least onevoltmeter electrically coupled to the at least one resistor and thesensing circuitry is configured to measure electrical resistances of thefirst pull wire based on a stimulation voltage applied to the first pullwire, an output voltage measured across the at least one resistor by theat least one voltmeter, and the known electrical resistance of the atleast one resistor.
 9. The articulatable elongate member of claim 1,wherein a distal portion of the first pull wire is electricallycouplable to a wire terminator positioned adjacent a distal portion ofthe shaft.
 10. The articulatable elongate member of claim 1, wherein thefirst pull wire comprise an electrically conductive material and anelectrical resistance of the first pull wire changes in response toplacing the electrically conductive material under tension.
 11. Thearticulatable elongate member of claim 1, wherein the shaft comprises aproximal portion and the sensing circuitry is positioned adjacent theproximal portion of the shaft.
 12. The articulatable elongate member ofclaim 1, further comprising a second pull wire enclosed within the shaftand coupled to the shaft such that a second application of tension tothe second pull wire bends the shaft, and wherein the sensing circuitrycomprises a first voltmeter and a second voltmeter, the first and secondvoltmeters corresponding to the first and second pull wires,respectively.
 13. The articulatable elongate member of claim 1, whereina measured increase in the electrical resistance of the first pull wireindicates an increase in tension or the breakage of the at first pullwire.
 14. A method of monitoring an articulatable elongate member, themethod comprising: measuring an electrical resistance of a first pullwire of the articulatable elongate member with a sensing circuitryelectrically couplable to the first pull wire as a first application oftension to the first pull wire articulates an articulatable portion ofthe articulatable elongate member; determining whether there is a changein tension or a breakage of the first pull wire based on the measuredelectrical resistance; and coupling the articulatable elongate member toa robotic driver and applying tension to the first pull wire with therobotic driver.
 15. The method of claim 14, wherein the sensingcircuitry is integrated with the robotic driver.
 16. The method of claim14, wherein the articulatable elongate member comprises the sensingcircuitry.
 17. The method of claim 14, further comprising: measuring anelectrical resistance of a second first pull wire of the articulatableelongate member with the sensing circuitry electrically couplable to thesecond pull wire as a second application of tension to the second pullwire articulates the articulatable portion of the articulatable elongatemember; determining whether there is a change in tension or a breakageof the second pull wire based on the measured electrical resistance; andcoupling the articulatable elongate member to the robotic driver andapplying tension to the second pull wire with the robotic driver. 18.The method of claim 14, wherein the sensing circuitry is electricallycouplable with the first pull wire and the first pull wire iselectrically couplable to a wire terminator to form a circuit comprisingthe wire terminator, the first pull wire, and the sensing circuitry. 19.The method of claim 16, wherein the articulatable elongate memberfurther comprises at least one resistor coupled to the at first pullwire, the at least one resistor having a known electrical resistance,and the circuit comprises the outer shaft, the first pull wire, the atleast one resistor, and the sensing circuitry.
 20. The method of claim19, wherein the articulatable elongate member further comprises a secondpull wire enclosed within the shaft and coupled to the shaft such that asecond application of tension to the second pull wire articulates thearticulatable portion of the shaft, and the at least one resistorcomprises a first resistor and a second resistor, the first and secondpull wires being couplable to the first and second resistors,respectively.